Alternating current signaling system



e '1, 1937. M; BAESECKE ET M. 2,101,699

ALTERNATING CURRENTSIGNALING SYSTEM Fil ed May' 26, 1954 i was 1:34

37 41 J a i, 45 a 42 #6 8 i as I fl rl'i n fies ecke incl 1951125 Wayei- 5 L%% 8 WM 1ft torneys Patented Dec; 7, a 1937 -"anrsnnsma schatt,Siemensstadt,

Application wcorporationofqermany; I VI I my 26, 1934, semi No. 127,606

i I a v 12,101,099 I J I I CURRENT; SIGNALING G r n AktiengesellnearGermany; u I

11 6mm" ar-302 I v r 1 4 Claims, I This invention relates to sig nalingwhich negative resistancesare employed duce the energy lossesoi'signalfcurrents. More fcontrol impulses overlong distances to theseveralparticularly this invention relates to alternating 5 current signalingsystems such as telephone or telegraph circuits, especially when thesignalcurrents are transmitted over long distancesplor inh stance .overunderground or. submarine cables. 3

Inparticular, thisinvention airords advantages 3 when crystals, powderresistances, suitable metal I alloys and soon are used as negativeresistances. oneQdifilculty which mustbe overcome in signaling' systemswith negative resistances is the supply and control of the currentbiasing the f hegative resistances to a suitable pointot their IIcharacteristic. Q'Ifhiscurrentis be transmitted over the Twholelsignalsystem whichcontains I widely 'difierentj, resistances, andjmustihave arelatively high input voltage; t According to the presentinventionspecial clrf cults are provided to I supply? thebiasing acin'rent to theseveral negativeresistances alonglthe lines. This supply circuit issoIdimensioned that a very goodinsulation exists between theindividualsupply conductorswith respect to the relatively high voltage at theendsof the supply circuit. t I [A generic feature of the severalspecific embodirnents whichwe have disclosed in this application, isfound in the fact that the voltage re telephone circuit. v I

" According to a further feature of our invention a separate line isprovided to supply the biasing for cable purposes." I

Another. feature or the ifnve onsists in rnployingparts of thesignaflinesor pecial cir cuits cooperating with se igqa 1mes,,forsupplying bias currenttto"the' negative resistances. Another feature ofthis inventonconsists in superposing "alternating current channels inthe signal current circuits to conduct the alternating currentto thepointsnat which negative resistances are located" and in rectifying thiscurrent to obtain a direct current for biasing purposes; This methodafl'ordsthe advantage that the biasquired for the production of thebiasing current is not applied between the two conductors oL aj currentto a pluralityof signalggimes especially ing current can be conductedover direct current a blocking devices, such asforinstance transtormfromthe ends or section points oithe lines. I In .(9131'8945) I I I I Iarticular, according to our-inventionthe biasing urrent-xitseli'u-may beemployed for transmitting,

negative resistances or to their control devices.

Further particularities otzthednvention will be i described 1hereinafterv with. reference .to the ;examples shown instnqiaccampanymgdrawing. 1 It i is to be understood that i the invention is not limited7 to the precise I conditions or proportions herein set forth; as theymay t bekreadily varied by thos'eskllled in the are I ,i Y ,i u 5 Fig. 1illustrates diagrammatically a system for supplying biasing currenttoatpluralityyof signal lines-by asingle separate line. I I I Fig. 2representsa system for supplyinga biasling current only y signal lineswithout disturbingthewsignal transmission; l t

1 P 8;- 3 shows the'supplyot biasing current from a separate line to atwo-wire circuit with parallel negative resistances, r it i Fig. 4 showsthe superposition of an alternating current for biasing purposes in asignal line. In Fig. 1 .we have illustrated a section of a pluralityoislines parallel to each other which are pr0vided f or. signal purpo efor instance this figure may represent a portion of a I telephone cable;For the sake-of simplieily'we hn've'shcw only two doublewire circuits fl2 and 3, 4 respec may. I 'rne portio suus f atea is subdivided, ag

indicatedby the v tical dash-dottedlines. into I threesubsectiohsinripihitzh negative resistances or well-known character,and, particularly, bodies of suitablesubstancesx'arearrangedin the con lby a capacity, indicated at, l6.

'I'heilatter as well astheIchokesare i to block the supply conductor 5and'the circuits,

withres pectto one anotheragainstvoice currents flowing through anegative resistance,

Energy losses and crosstalk aretthuslprevented Instead of simple chokes,networksmay belprovided, preferably with a short circuiton the sidemiddle (andfthefl 3. f i y I right portions ofFigglshowfthe sam a r ge;Q mht 1 ea h fj hasubsection a's-thenheiatthef of the I supply.conductor. The

extreme left. At the points l1, II we have indicated by the dotted linesthat two further wire circuits may be connected to the supply conductorin the same number. For the return of the biasing direct current we mayuse a separate conductor or ground connections.

Particularly when using cables, the cable sheathing or the sea water mayserve as the return conductor.

As shown in Fig. l, the negative resistances of one conductor areconnected in series with respect to the biasing current, that is, thetwo ends of the negative resistances are connected to the same conductorof the supply circuit. According to our invention, it may be preferredin some cases to connect the negative resistances belonging to onecircuit, alternately or in any other desired order to one or the otherconductor of the supply circuit, in which case a separate conductorwould be provided for each direction of the supplying current. Thenegative resistances may be also connected in parallel to thesupplyconductor with respect to the same points of view as above described, toblock the supply circuit against the signaling currents. The adjustmentof the working points of the negative resistances may be effected byseries or parallel connection of separate resistances or by suitabledimensioning of filters, or even when the same relations exist in allcircuits, by connecting resistances in the supply circuit or by suitabledimensioning of the supply circuit. When using the invention for longdistance lines, particularly in the case of parallel lines as in acable, a preferable arrangement might be to provide several supplycircuits or to arrange a main supply circuit and branch off atpredetermined intervals, sub-supply circuits supplying biasing currentto the corresponding sections. A supply circuit with a separate sourcemay also be provided for several sections of a line or of a bunch ofcircuits.

To prevent a flow of the biasing current through the signal conductorsfrom the two sides of the negative resistances, according to Fig. 1 thesections of these conductors between the negative resistances areblocked against the biasing current by capacities, such as indicated atl9, 2|) and 2|, 22 respectively, having only a low resistance to thepassage of the signal currents. To enable a flow of direct current or oflow frequency alternating currents for signal purposes through theconductors I and 4, suitable by-pass connections are provided. In Fig. 1simple chokes 23, 24 are indicated for this purpose. These must bedimensioned to offer a high resistance to currents of higher frequenciessuch as, for instance, voice currents.

According to a further feature of our invention the two wires of asupply circuit are strung or arranged in such a manner that they will beseparated from one another by insulation adequate with respect to thedirect current voltage. Particularly in the case of cables, the twowires of the supply circuits are arranged in different parts of thecable, for instance in different wiregroups which are very wellinsulated from each other. I

In those cases where the mutual influence of the circuits traversed bythe signal currents, for instance the cross talk in cables, is to bereduced to a minimum, asymmetrical distribution of the negativeresistancesover the two conductors of a circuit is a preferablearrangement. It has been found that the mutual influence of the circuitscan be diminished still more if the direction of the biasing current inthe two conductors is chosen properly. According to our invention it ispreferable to make the biasing current flow through the two conductorsof a cable or open line circuits with negative resistances in the samedirection in each of the conductors. This method aflords specialadvantages with lines having Pupin coils for damping attenuation, inaddition to including negative resistances, because the Pupin coils arebiased magnetically in case the biasing current flows through the twoconductors in different directions, that is, with respect to the signalcurrent. The biased Pupin coils would diminish. their attenuating effectand magnify the cross talk. Preferably, .the biasing current is suppliedto the two-wire circuit at symmetrical points, for instance over themidpoint taps of transformers, chokes or other cross resistances, and isagain taken off at such points.

Examples of such arrangements are illustrated by Figs. 2 and 3.

In Fig. 2 two double-wire circuits, for instance those of a telephonecable having conductors 25, 26 for transmission in one direction andconductors 21, 28 for transmission in the other direction, are shown asconnected with the line terminals by transformers 29, 30 and 3|, 32respectively. The midpoints of the transformer windings connected to theline are at the one end of the line connected to a battery 33, and atthe other end of the 'line to a battery 34 supplying the biasing currentto the negative resistances 35 46 connected in the line. The conductors25, 26 and 21, 28 respectively are traversed, substantially as in aphantom circuit, by the biasing current which flows in the samedirection in both conductors of the same pair, whereby the symmetry ismagnified considerably. The line section extending from the one or theother end of the whole line to the next pair of negative resistances 35,36 and 31, 38 or 43, 44 and 45, 46 respectively is suitably equalized toone half of the length of the other line sections for instance 35, 3936, 40. In this manner an easy connection of lines may be effected.

Fig. 3 represents an arrangement for supplying the biasing current by aseparate conductor. To the terminals of the negative resistances 48, 49arranged symmetrically in the two conductors 51, 58 of a two-wirecircuit, are connected the chokes 50, 5| which connect the said twoconductors to one another. From a third conductor 41' the biasingcurrent is supplied to the negative resistances through the said chokes.The capacities 53-56 serve to prevent a flow of direct current throughthe conductors 51, 58. On

the other hand, a capacity 52 is arranged to provide a short circuit forany signal currents which may flow through the chokes 5|], 5|.

Instead of a separate line such as described above, a phantom circuitmay be employed as a common supply circuit for a plurality of lines. Inall cases it is preferable to employ side circuits at a considerabledistance from one another in the bunch, in view of using a high inputvoltage. To cause the biasing current to flow through the conductor inthe same direction, it is also possible to shunt all conductors withrespect to the biasing current by cross resistances or equivalentelements and to employ a common return conductor. The latter may be aseparate conductor, or the cable sheathing, or the earth, or seawater.

In many cases it is not possible to conduct a direct current as abiasing current along the lines A resistances orover those parts :oftheline which.

on account of-interference from foreign sources, such as power currents.In such cases it is preferable lto bloclr the line or sectionsof theline p by transformers. fhFor. other reasons aswell, for

instance when using amplifiers or capacitive couplings in the line, ,adirect currentflow can be prevented.

According to" one, feature or embodiment of [our invention analternating current is. corfducted to the points at which there arenegative do notpermitaflow of direct currentgand is rectified beforebeing: supplied to the "negative resistances. Thealternating currentsource may I belocated at the endof the line or of the subsection of theline, 'orconnected to separate conductors provided: for supplying thebiasing curwrent. PreferablyQthe rectificationis-eflected bycontactdevices, forflinstance dry rectiflersor in, ,any other well knownor approved mannen For this purpose we may use negative resistances of pthe same character. as those provided for reduc ing the attenuation ofthe line.. an example of'such anarrangement.

Fig. 4 shows 1 -At 53 we haveindicateda longdistance line,

for instance a submarine cable havingonly one conductor, the returnconductor-being replaced by;sea-water.- At 8|, Bland ",lflrespectively,

we have indicated. the terminal transformers to the primary windingsofwhich standard .or approved apparatus, for instance any well-knowntelegraphy apparatus, are. connected. .The line .59 1 is subdividedinto;several sections, eachhaving a repeaterstation formed by connectionswith negativeresistances such as the one, indicated at 'lLmLet, us.assume that thetelegraph cur- .rent has a frequency at the lower limitof audio-freqi' ency,and that for biasing thev negw filter 65, capacity15, negativeresistancelkcaa ti ve resistances .there is superposed onthe line 59 an alternating currentwhich-has a frequency below :theaudio-frequency band. In the station 60 the telegraph current flowsthrough the pacity. I6 and rfilterwaflback to the line section between60 and 6|; The .filter 64 does'not permit passage of the telegraphcurrent but of the superposedtbiasing current, so that the latter flowsthrough the primary winding Ill ofa transformer, the secondary windingof which is connected to a rectifier 12; The rectified alternating,current is supplied over the chokes 11;" to the negative resistance IIand acts as abiasing current. The capacity: 13 servesasa short circuitfor audio-frequency currents coming over 11,18. Ina parallel lbranch,thealternating current from the filter 64 flows through the filter l9and furthermore to the line 59;: The filters 64 and 19 do not permit thepassageof audio-frequency. currents and are earthed by theconductors 66,68. The superposed current for biasing purposes ,might also be in therange of upperaudio-frequencies.

According to a further feature of our inven- -tion, in linescontainingnegative resistances for reducing the energy losses, means are providedby which the negative resistances can be controlled or switched'in orout. This arrangement is particularly advisable in the case of longlines. These means can be adjusted manually or automatically and locatedat the termlnalsof the lines or in subsections of the lines. In thelatter case a remote control is desirable." r

In the simplest embodiment of ourinvention, the biasing current flowingthrough the line is controlled for all negative resistances at the Iterminals of the lineor at any other .pointof the line. This permitsacommon variation of the attenuation to be effected for the whole line.Regulation may be effected by varying thevoltage of the biasing currentor-by yarying the resistanceof a branch .of the biasing circuitpnottraversed by the signal current. Foninstance, Y

as indicated in Fig. 2, theconnection ,of the. batteries 33 and 34 iwith the coils of the respective transformers. may be adjustable, thearrows being theconventional representation ofcontrollers or slideswhich can be moved to different points: of thelsaidcoils. v When theline issubdivlded into several sections and a separate biasing source is1 provided for every section, the same arrange ments can be made.Another possibility consists .in apportioning or attaching'to every'negative resistance the value of which islto' be controlled,

or. to a groupof such resistances, a special operatlng device, forinstance a selectiveswitch-,: by which it, is possible-to effect avariation of the resistance values, for example a switching in or out(Of :the resistances By such an operatingdevice 2. parallel" resistancescan hex-switched in -or out in steps, for instancethebiasing current orthe signal currentmay be conducted over this parallel circuit. Thevariation .of the negative reisistances can be aiso efl'ected in acontinuous mannerwforc instance by influencing continuously changeablepositive resistances connected to the'negative resistances. The saidregulatingdevices can be controlled in any-well-khown :manner from theterminals of the. line, or from supervisory'stations atother points ;ofthe line, or in dependence upon" the attenuation of the line; Accordingto a further feature of our invention, we may employ the biasing currentitself forthe remote controlof the regulating device, by transmittingimpulses for a short time by means of this current, .whe're" by forinstance a selective switch is controlled. 1 Using alternating currentas the biasing current for the negative resistances rec ifledat thepoints where negative resistances are located, switching apparatus canbe controlled selectively fby varying the frequency of thealternatingcurrent in a well-known manner. 'It is also wi hin the scopeof our invention to employ for the'reniote con- 'trol, separate lines orchannels over which the control of 'theregulating dvices is eilected byalternating or direct current.

i What weclaim isz" j N .1. A signaling system comprising lines forsignal transmission, said lines extending from a transmitting station toa receiving station, negative resistances connected in these lines atdiiferent distances from the endsjof the lines, for reducing the loss ofsignalenergy, and especial line extending lengthwise oi' the signalingsystein and connected .with aplurality' of said signal lines forsupplying currents to bias the negative resistances.

2. A cable circuit, comprising lines for signal resistances connected inthese lines at difl'erent distances from the ends of the lines, forreducing theloss of signal energy, a,source of bias current, a separateconductor for supplying said bias current to said negative resistances,and separate means for the return of the bias current to its source.

3. A cable circuit comprising lines for signal transmission, said linesextending from a trans,- mitting station to a receiving station.negative transmission, said lines extending from a transmitting stationto a receiving station, negative resistances connected in linesatdifferent distancesfrom the endsoi the lines, .flirnireglucing the lossof signal energyj'a source oi'biascurrent, and a two-wire circuitior'supplying said bias current to said negative resistances, thetwowires of said circuit within the cable being well separated from eachother electrically.

4. A signaling system comprising a signal line extending from atransmitting station to a receiving station, negative resistancesconnected in said line at different distances from its ends, forreducing the loss of signal energy, a separate line for supplyingbiasing current to said negative resistances, filters interposed betweenthe said biasing current line andthe signal line to block the signalcurrents, and devices located in the signal line on either side of eachnegative resistance, to block the biasing current.

5. A signaling system comprising a signal line extending from atransmitting station to a receiving station, negative resistancesconnected in said line at different distances from its ends, forreducing the loss of signal energy, and a separate line for supplyingbiasing current to said negative resistances, each side of a negativeresistance being connected with the same-conductor of said separateline.

6. A signaling system comprising two signal lines each composed of twoconductors, negative resistances connected in said conductors, and aseparate current supply circuit for biasing the said negativeresistances, the two conductors of one signal line being connected inparallel for leading the biasing current in the one direction, and thetwo conductors of the other signal line being connected in parallel forleading the biasing 'current in the other direction.

7. A signaling system comprising a cable containing two signal lineseach composed of two conductors and well separated electrically from theother line, the two conductors of the same line being connected inparallel, negative resistances connected in said lines, and means forsupplying biasing currents to said negative resistances, said biasingmeans being connected to each of said four conductors.

8..A signaling system comprising a signal line composed of twoconductors, negative resistances connected in saidconductors atcorresponding points thereof, cross-connections between said conductorsto connect them in parallel at the two terminals of said negativeresistances, and a separate line, connected with said cross-connections,for supplying biasing current to said negative resistances.

9. A' signaling system comprising a signal line, negative resistances insaid line, a source of current for biasing said negative resistances,and a single controller, connected in series with a pluralityoi saidresistances for varying the voltage of "said' biasing current in suchplurality of resistances.

10. A signaling system comprising a signal line, negative resistances insaid line, a source of current in circuit with said negative resistancesfor biasing the latter, and a single controller, connected in serieswith all the resistances in said circuit, for varying the resistance ofthe circuit through which said biasing current flows through all of saidresistances. A

11. A signaling system comprising a plurality of independent electricalcircuits for signal transmission, each circuit having conductorsextending from a transmitting station to a receiving station, negativeresistances connected inthese conductors for reducing the loss of signalenergy, and means for supplying currents to bias the negativeresistances, saidmeans including auxiliary conducting means connectedbetween said conductors and connected to a source of current to form anelectrical circuit through said resistances and substantiallycoextensive with said system.

12. A signaling system comprising atplurality of independentelectricalcircuits fqr sigjnal transmission, each circuit havingconductors extending from. a transmitting station to a receivingstation, negative resistances connected in these conductors for reducingthe-loss oi;sig'nal energy,

and means for supplying cur'rentsl' to bias the negative resistances,said means including current supply means,- auxiliarycurrentlconducting" conductors for reducing the loss oi signal energy, 7

and means for supplying currents to bias the negative resistances, saidmeans including unidirectional current supply means connected to saidconductors for passing the biasing current at least through parts ofsaid conductors and to form electrical circuits through said resistancesand substantially coextensive with said system.

14. A signaling system comprising a plurality of independent electricalcircuits tor transmitting separate signals between stations,- eachcircuit having a conductor with ,negative gesistances connected thereinto redu'cefthe lossoi vsignal en ergy, and means to supply current tobias said resistances, said means comprising a source of bias currentand means connecting said source with each of said independent circuits.

MARTIN BAESECKE.

HANS MAYER.

